We have made topographical map and analyzed distribution pattern of tidal flats in riverine estuaries of 16 rivers. Making use of the topographic map and other information, we selected the part of straight channel of 16 rivers and classified those into three areas from a viewpoint of the morphology of sand bar, that is, alternating sand bar, double mode bar, or no sand bar. Furthermore, we have calculated various physical parameter values which can affect the topography of river channel assuming the event of mean annual maximum water discharge and analyzed relationship between morphology of sand bar and those values. In the result, we showed the morphology of sand bar has strong relationships with river channel width/depth ratio at mean annual maximum water discharge but the border line between alternating sand bar and double mode bar is more vague than that in upper alluvium river channel.